eval function

Tony1 has asked for the wisdom of the Perl Monks concerning the following question:

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Re: eval function by kyle (Abbot) on Apr 13, 2007 at 14:57 UTC
Have you read the eval documentation? Do you have any specific questions after reading it? Is there a particular problem you're trying to solve?	[reply]
Re^2: eval function by Tony1 (Novice) on Apr 13, 2007 at 15:28 UTC
hai i a had read it but i and also understand some how but it's not working while using eval in my perl programming i want to know the meaning of the eval function	[reply]
Re^3: eval function by Joost (Canon) on Apr 13, 2007 at 15:49 UTC
I dont want to be condescending, but could you restate that in some form that makes sense? (Programming) languages have no meaning, they're tools. "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply]
Re^3: eval function by dynamo (Chaplain) on Apr 13, 2007 at 15:49 UTC
What did you try that didn't work? Here are some examples that might help: `# this prints "something" with extra layers of pointless recursion: print (eval (eval (eval (eval (eval (eval "something"))))); # prints 1024 $it = "ev"."al (".substr("devaluation",1,4) . "(2+2)" .""x2 . " 3)"; foreach (0..3) { $it = "eval($it) 2" } print eval($it);` [download]	[reply] [d/l]
Re: eval function by dynamo (Chaplain) on Apr 13, 2007 at 15:30 UTC
Eval is a method that allows you to run dynamically generated (or dynamically retrieved) code. Generally, I view it as a masochistic feature of the language, try not to use it unless you really need to (there is almost always a way to get around it). Most applications I have seen that really require eval fall under the heading of Stupid Perl Tricks. It is often used to confuse, impress, and/or scare other perl programmers; or to break rules. What's your goal and why do you think it might require eval?	[reply]
Re^2: eval function by doom (Deacon) on Apr 13, 2007 at 21:46 UTC
Generally, I view it as a masochistic feature of the language, try not to use it unless you really need to (there is almost always a way to get around it). Most applications I have seen that really require eval fall under the heading of Stupid Perl Tricks. There's no other way to do error trapping in perl. If you want to intercept a "die/croak" in someone else's code and handle it yourself, you need to use eval. Myself, I like to do things like: `use Test::More; SKIP: { eval { require DBD::SQLite }; skip "DBD::SQLite not installed", 3 if $@; # 3 is "how many to skip" # ... tests using SQLite }` [download]	[reply] [d/l]
Re^3: eval function by ikegami (Patriarch) on Apr 13, 2007 at 22:43 UTC
dynamo was talking about `eval EXPR`. You are talking about `eval BLOCK`. Despite the similariry in their name, they are two very different functions with very different purposes.	[reply] [d/l] [select]